Fine processing of a semiconductor substrate by lithography using a photoresist has been performed in the production of semiconductor devices. The fine processing is a processing method including: forming a thin film of a photoresist on a semiconductor substrate such as a silicon wafer; irradiating the resultant thin film with an active ray such as an ultraviolet ray through a mask pattern in which a pattern of a semiconductor device is depicted for development; and etching the substrate by using the resultant photoresist pattern as a protecting film so as to form fine convexo-concave shapes corresponding to the pattern on the surface of the substrate. Recently, however, high integration of semiconductor devices has progressed and the active ray used tends to have a shorter wavelength, such as an ArF excimer laser (193 nm) replacing a KrF excimer laser (248 nm). Following such a tendency, the influence of reflection of an active ray on a semiconductor substrate has become a major problem. Thus, in order to solve this problem, a method of providing a bottom anti-reflective coating between the photoresist and the substrate has been widely studied. For such a bottom anti-reflective coating, many investigations on an organic bottom anti-reflective coating composed of a polymer having a light absorbing group and the like are performed due to easy use and other reasons. Examples of the coating include an acrylic resin-based bottom anti-reflective coating having both a hydroxy group as a crosslinkable group and a light absorbing group within a single molecule thereof, and a novolac resin-based bottom anti-reflective coating having both a hydroxy group as a crosslinkable group and a light absorbing group within a single molecule thereof.
Examples of the characteristic required for the bottom anti-reflective coating include: having a large absorbance to light or radiation; causing no intermixing with a photoresist (being insoluble in a photoresist solvent); causing no diffusion of low molecule substances from the bottom anti-reflective coating to the photoresist as the upper layer during heating and baking; and having a dry etching rate higher than that of the photoresist.
Furthermore, in recent years, in order to solve a problem of wiring delay that has become apparent as the application of a finer design rule of semiconductor devices has promoted, it has been studied to use copper as a wiring material. Along with that, a dual damascene process has been studied as a wiring forming method for a semiconductor substrate. For this reason, in the dual damascene process, a bottom anti-reflective coating is formed on a substrate having a large aspect ratio in which a via hole is formed. Therefore, the bottom anti-reflective coating used in this process is required to have filling characteristics capable of filling holes without voids, planarization characteristics capable of forming a planar film on the substrate surface, and the like.
As an intermediate film between the semiconductor substrate and the photoresist, a film known as a hard mask containing a metal element such as silicon and titanium (see, for example, Patent Document 1) is used. In this case, the resist and the hard mask have components largely different from each other, so that the removal rates of the resist and the hard mask by dry etching largely depend on the type of a gas used for dry etching. Then, by appropriately selecting the type of a gas, the hard mask can be removed by dry etching without a large decrease in the film thickness of the photoresist.
Thus, in the production of semiconductor devices in recent years, for achieving various effects such as anti-reflection effects, a resist underlayer film has become disposed as an intermediate layer between the semiconductor substrate and the photoresist. Then, also until today, the studies of a composition for a resist underlayer film have been performed. However, due to the diversity of characteristics required for the composition and the like, the development of a novel material for the resist underlayer film is desired.
For example, there is disclosed a composition or a pattern forming method using a compound having a silicon-silicon bond (see, for example, Patent Document 2).
There is disclosed a bottom anti-reflective coating forming composition containing an isocyanate group or a blocked isocyanate group (see, for example, Patent Document 3).
There is disclosed a hard mask material using a polycarbosilane-containing resin (for example, Patent Document 4 and Patent Document 5).
There is disclosed a silica-based coating film forming composition containing a siloxane polymer, a solvent, and a cyclic basic compound (see, for example, Patent Document 6 and Patent Document 7).